Festivalgoer took up to nine MDMA capsules

A young man who took up to nine MDMA capsules at a Sydney music festival told his friend "he was just going to keep a strong mind and push through it" before he collapsed and died, an inquest has heard.

Passionate musician and AFL player Callum Brosnan, 19, became unresponsive at Olympic Park train station after attending the Knockout Games of Destiny electronic dance music event in December 2018.

He died in hospital within hours as a result of MDMA and cocaine toxicity.

Mr Brosnan took between six-and-a-half and nine capsules at the event, Detective Inspector Karl Reis told the inquest on Tuesday.

The police officer said one capsule later found in the teenager's bum bag was tested and contained MDMA at a high purity of 77 per cent.

One of his friends, who can't be identified for legal reasons, gave evidence that they bumped into each other about 5pm and stayed together for most of the festival.

He understood Mr Brosnan to previously ingest MDMA once or twice a month, adding that on "most occasions" those in their peer group took multiple capsules.

He said by 9pm Mr Brosnan had told one of their friends he'd had seven MDMA capsules.

Mr Brosnan seemed fine and dancing, singing and performing shows for other patrons with his light-up gloves, the friend told the NSW Coroners Court.

"We believe he could've got more pills for doing these shows for people but that's not something we can confirm."

He said usually people would offer something as a reward for the displays.

But by about 11.30pm Mr Brosnan was "standing there, staring at the stage, looking blank", he said.

"I asked if he needed a break or some water and he said 'no'."

He said Mr Brosnan's comment about pushing through made him think "he'd be alright" but he stumbled on the way to the station after the event and was found talking to "some random people" who couldn't understand him.

Paramedic Brae Pettiford said Mr Brosnan was fitting when they arrived and never regained consciousness.

He went into cardiac arrest on the way to Concord Hospital.

The friend told the coroner if he could speak to his younger self he would have made Mr Brosnan get medical help, fresh air or some rest - "whatever could have helped".